1. FIELD OF THE INVENTION
This invention relates to in-pipe running robots, and more particularly to an in-pipe running robot for use in various operations inside piping such as inspection of interior conditions or repair of inner walls of piping. The invention relates also to a method of running such a robot.
2. DESCRIPTION OF THE RELATED ART
In order to inspect and repair piping interiors, such an in-pipe running robot is required to run straight along a piping axis, and to run round circumferentially in the piping while adhering to an inner wall and maintaining a fixed position axially of the piping.
The robot runs straight along the piping axis, for example, to arrive at an intended location quickly or to inspect piping bottoms successively which, generally, are the most susceptible part of the piping. Where the piping includes a welded joint formed circumferentially thereof, for example, the robot is required to run circumferentially in the piping to inspect or repair the joint as necessary.
This type of in-pipe running robot has adherent wheels to be able to run while adhering to running surfaces in vertically extending piping as well, for example.
FIG. 6 (a) shows a running state of a conventional in-pipe running robot. This in-pipe running robot includes a vehicle body movable inside piping along a piping axis, and a pair of front and rear running devices attached to the vehicle body. Each running device includes a pair of wheels mounted on opposite end regions of an axle, and is steerable about a vertical axis of the vehicle body. The center of steering extends linearly in a fore and aft direction of the vehicle body. The robot further includes drive control devices for individually driving the pair of running devices, and steering control devices for individually steering the running devices.
When the robot is required to run straight along the piping axis, the vehicle body and running devices are placed in the posture shown in FIG. 3 (a) (with the fore and aft direction of the vehicle body extending parallel to the piping axis, and the axles of the running devices extending at right angles to the piping axis). When the robot is required to run round the piping axis, the vehicle body and running devices are placed in the posture shown in FIGS. 3 (b) and 6 (a) (with the fore and aft direction of the vehicle body extending parallel to the piping axis, and the axles of the running devices aligned to each other and extending parallel to the piping axis).
Conventionally, the in-pipe running robot is intended to maintain a fixed position axially of the piping in running round circumferentially in the piping. However, as shown in FIG. 6 (a), the robot would turn over by gravity when the robot becomes tilted to a certain degree.
It is therefore necessary with the robot having the above construction to rely on the adhering ability of the running devices for an appropriate selection of the center of gravity of the robot, or to limit a load capacity of the robot. This presents restrictive conditions in designing of the robot, which are undesirable.